API: preprocessing.imputation

skyulf.preprocessing.imputation

Imputation nodes (Simple / KNN / Iterative).

Each Applier/Calculator dispatches on engine via apply_dual_engine / fit_dual_engine (see dispatcher.py). Per-engine logic lives in small _apply_polars / _apply_pandas / _fit_polars / _fit_pandas static helpers so the public apply / fit methods stay at CCN 1 (Codacy lizard_ccn-medium).